1. Field of the Invention
This invention relates to a barrel-polishing apparatus and a barrel-polishing method.
2. Prior Art
(First Prior Art and Shortcomings Thereof)
In conventional barrel-polishing apparatuses, it is a usual practice that a workpiece is polished while flowing polishing mediums or while vibrating a workpiece in stationary polishing mediums.
However, because of the reasons that the polishing mediums tend to bulge over the workpiece due to flow of the polishing mediums in the former polishing apparatus and due to flow of the polishing mediums caused by vibrations of the workpiece in the latter polishing apparatus, a surface pressure of the polishing mediums applicable to the workpiece is readily reduced to discourage the enhancement of the polishing efficiency.
(Second Prior Art and Shortcomings Thereof)
Conventionally, there is known a typical method for polishing a workpiece. In this method, a workpiece is placed in polishing mediums such that an upper end side of a surface-to-be-polished of the workpiece is slanted forwardly and the workpiece is polished by rotating the workpiece in a circumferential direction while flowing the polishing mediums relative to the workpiece.
However this conventional barrel-polishing method has such shortcomings that in case the workpiece has a hole around its axis, the polishing mediums readily pass through the hole when they flow along the workpiece and therefore, they hardly stay at the axial portion of the workpiece, with the result that the axial portion of the workpiece is left unpolished.
(Third Prior Art and Shortcomings Thereof)
In the conventional barrel-polishing apparatus, it is a usual practice that a workpiece is polished while flowing the polishing mediums.
However, this conventional barrel-polishing apparatus has such shortcomings that since the entire polishing mediums must be flowed in order to flow the polishing mediums, the apparatus itself inevitably becomes large scale.
(Fourth Prior Art and Shortcomings Thereof)
If the workpiece is polished while rotating the workpiece in the polishing mediums, the polishing mediums are worn. Therefore, in the conventional apparatus, when the aggregate of polishing mediums has been partly worn, the workpiece is moved in the polishing medium bath in an effort to find a non-worn part of the polishing mediums and dipped in the non-worn part of the polishing mediums. By keep doing so in the polishing operation, a certain polishing effect can be obtained.
However, in such a conventional polishing apparatus, since the partial wear of the aggregate of polishing mediums is determined based on the perception or experience of the operator, much labor is required. In addition, since the result of determination is different depending on each operator, a constant polishing effect is difficult to obtain in an efficient manner.
It is the first object of the present invention to provide, in order to obviate the shortcomings inherent in the first prior art, a barrel-polishing apparatus having flowing polishing mediums, wherein a pressure level of polishing mediums applicable to a workpiece is maintained to a predetermined value or larger by preventing the polishing mediums from bulging, thereby enhancing the polishing efficiency of the barrel-polishing operation (hereinafter referred to the xe2x80x9cfirst and second inventionsxe2x80x9d).
It is the second object of the present invention to provide, in order to obviate the shortcomings inherent in the second prior art, a barrel-polishing method, wherein polishing mediums are primarily stayed at an axial portion of the workpiece so that a peripheral edge portion and the axial portion of the circumferentially rotating workpiece can be polished efficiently and positively (hereinafter referred to the xe2x80x9cthird to fifth inventionsxe2x80x9d).
It is the third object of the present invention to provide, in order to obviate the shortcomings inherent in the third prior art, a barrel-polishing apparatus, which is simple in structure and easy in maintenance (hereinafter referred to the xe2x80x9csixth and seventh inventionsxe2x80x9d).
It is the fourth object of the present invention to provide, in order to obviate the shortcomings inherent in the fourth prior art, a barrel-polishing apparatus, wherein a constant polishing effect can normally be obtained efficiently and automatically even in case an aggregate of the polishing mediums is partly worn (hereinafter referred to the xe2x80x9ceighth inventionxe2x80x9d).
(Construction of the Invention and Operation and Effects Thereof)
A barrel-polishing apparatus according to the first invention comprises a polishing medium bath with polishing mediums received therein, a base, an arm mounted on the base, and a workpiece attachment device mounted on a distal end portion of the arm and adapted to attach a workpiece to the arm, wherein the polishing mediums are caused to flow within the polishing medium bath by appropriate means and a pressing plate for pressing the polishing mediums is mounted on the polishing medium bath. Accordingly, since the polishing mediums are prevented from bulging by this pressing plate, a pressure level of the polishing mediums applicable to the workpiece can easily be maintained to a predetermined value or larger in the barrel-polishing apparatus having flowing polishing mediums. Thus, with use of this barrel-polishing apparatus, the polishing efficiency of the barrel-polishing operation can easily be enhanced in the barrel-polishing apparatus having flowing polishing mediums.
Also, as in the barrel-polishing apparatus according to the second invention, if there are further employed vibration means for vibrating the arm and a pressing plate for pressing the polishing mediums, mounted on the polishing medium bath, the polishing mediums are prevented from bulging by this pressing plate. Accordingly, a pressure level of the polishing mediums applicable to the workpiece can easily be maintained to a predetermined value or larger in the barrel-polishing apparatus having a vibrating workpiece. Thus, with use of this barrel-polishing apparatus, the polishing efficiency of the barrel-polishing operation can easily be enhanced in the barrel-polishing apparatus having a vibrating workpiece. If the pressing plate is fixed to the base and the polishing medium bath is moved reciprocally in a direction of the work attachment device by reciprocal means, or if the pressing plate is fixed to the base and the pressing plate is pressed in a direction of the polishing medium bath by pressing means, a pressure of the pressing plate applicable to the polishing mediums can be adjusted. Accordingly, a surface pressure of the polishing mediums applicable to the workpiece can be adjusted appropriately.
Also, if the pressing plate is divided into a plurality of auxiliary pressing plates and a pressing state of each of the auxiliary pressing plates is adjustable, a surface pressure of the polishing mediums applicable to a surface-to-be-polished of a single workpiece can partly be adjusted.
Also, if the arm is swung about the base with respect to an inner wall surface or an inner bottom wall surface of the polishing medium bath by swing means such that the arm can be fixed at an appropriate location, the surface pressure of the polishing mediums applicable to the workpiece can be adjusted by varying the flow rate of the polishing mediums relative to the workpiece.
Also, if the arm is axially reciprocally moved by reciprocal means so that the arm can be fixed at an appropriate location, the depth of the workpiece with respect to the polishing mediums can be adjusted. Thus, the surface pressure of the polishing mediums applicable to the workpiece can be adjusted.
Also, a barrel-polishing apparatus according to the third invention comprises a polishing medium bath with polishing mediums received therein, a base, an arm mounted on the base, a workpiece attachment device mounted on a distal end portion of the arm and adapted to attach a workpiece to the arm, and a pressing plate mounted on the polishing medium bath and adapted to press the polishing mediums, the polishing mediums being flowed relative to the workpiece within the polishing medium bath, wherein the pressing plate is disposed at an upper portion of the workpiece with an appropriate space therebetween. Accordingly, since the polishing mediums are prevented from bulging at its area above the workpiece by the pressing plate, the surface pressure of the polishing mediums applicable to the workpiece can be maintained at a level of a predetermined value or larger. Thus, with use of this barrel-polishing apparatus, the polishing efficiency of the barrel-polishing operation can easily be enhanced in the barrel-polishing apparatus having flowing polishing mediums.
If the pressing plate is provided with a recess so that an upper portion of the workpiece is surrounded by the recess with an appropriate space therebetween, the polishing mediums can be prevented from escaping sidewardly of the workpiece. Therefore, the surface pressure of the polishing mediums applicable to an upper surface and a side surface of the workpiece can be prevented from escaping, thereby the surface pressure can easily be maintained at a level of a predetermined value or larger. In addition, since the flow of the polishing mediums relative to the workpiece can be straightened, the workpiece can easily be rubbed. As a consequence, the workpiece can be polished in a satisfactory manner.
Also, if, in this barrel-polishing apparatus, a guide plate is connected to that end edge of the pressing plate located on an upstream side of the polishing mediums, and the guide plate is slanted towards the upstream side of the polishing mediums in an opposite direction to the workpiece, the polishing mediums can easily be gathered to the inner side of the pressing plate.
If, in this barrel-polishing apparatus, the pressing plate is fixed to the base and the polishing medium bath is reciprocally moved in a direction of the workpiece attachment device by reciprocal means, or if the pressing plate is mounted on the base and the pressing plate is pressed in a direction of the polishing medium bath by pressing means, the pressure of the pressing plate applicable to the polishing mediums can be adjusted. Thus, the surface pressure of the polishing mediums applicable to the workpiece can appropriately be adjusted.
Also, a barrel-polishing apparatus according to the fourth invention comprises a polishing medium bath with polishing mediums received therein, a base, an arm mounted on the base, a workpiece attachment device mounted on a distal end portion of the arm and adapted to attach a workpiece to the arm, and a pressing plate mounted on the polishing medium bath and adapted to press the polishing mediums, the polishing mediums being flowed relative to the workpiece within the polishing medium bath, wherein the pressing plate is disposed at an upper portion of the workpiece with an appropriate space therebetween, and a baffle plate is connected to a distal end side of the pressing plate in such a manner as to cover the workpiece. Accordingly, the polishing mediums collided against and raised along the surface-to-be-polished of the workpiece invade into a space surrounded by the pressing plate and the baffle plate and causes a turbulent flow involving the vicinity of the surface-to-be-polished of the workpiece. Accordingly, the polishing efficiency with respect to the workpiece is enhanced.
Also, in a barrel-polishing apparatus in which a workpiece is disposed in polishing mediums such that the workpiece can be rotated in a circumferential direction, an upper end portion of a surface-to-be-polished of the workpiece facing a relative flowing direction of the polishing mediums is slanted forwardly and the workpiece is polished while flowing the polishing mediums relative to the workpiece, a barrel-polishing method according to the fifth invention comprises the step of adjusting the flowing speed of the polishing mediums relative to the workpiece. Accordingly, the polishing mediums can be primarily stayed at the axial portion of the workpiece by reducing the relative flow rate of the polishing mediums. Thus, with use of this barrel-polishing method, the peripheral edge portion and the axial portion of the circumferentially rotating workpiece can be polished efficiently and positively.
If the flowing of the polishing mediums relative to the workpiece is stopped in accordance with necessity, the polishing mediums can be primarily stayed more positively. Thus, the axial portion of the workpiece can be polished more efficiently.
Also, if the flowing of the polishing mediums relative to the workpiece is stopped at the first or last stage of a polishing operation, an arrangement of the polishing operation becomes easy and therefore, the efficiency of the polishing operation is enhanced.
The relative flow of the polishing mediums with respect to the workpiece includes a method for flowing the polishing mediums and a method for moving the workpiece.
Also, a barrel-polishing apparatus according to the sixth invention comprises a polishing medium bath with polishing mediums received therein, a base, rotational drive means mounted on the base, a rotary shaft mounted on the rotational drive means, and a workpiece attachment device mounted on a distal end portion of the rotary shaft and adapted to attach a workpiece to the rotary shaft, wherein the barrel-polishing apparatus further comprises vibration means, and the rotary shaft is circularly vibrated by the vibration means along a plane including an axis of the rotary shaft. Accordingly, the polishing mediums can be moved into and out of the recess of the workpiece even in the state that the polishing mediums are stopped. Therefore, with use of this barrel-polishing apparatus, it becomes only needed to vibrate the rotary shaft instead of flowing the polishing mediums. Thus, the polishing apparatus itself is simplified in structure and its maintenance becomes easy.
As shown in a barrel-polishing apparatus according to the seventh invention, instead of vibrating circularly, the rotary shaft may be vibrated forwardly and backwardly, leftwardly and rightwardly.
Also, if a slide plate is mounted on the base such that the slide plate is reciprocally moved in a direction of the polishing medium bath by reciprocal means and the rotational drive means is mounted on the slide plate, the rotary shaft and thus the workpiece can be vibrated circularly, or forwardly and backwardly, and leftwardly and rightwardly. Since the polishing mediums can be more easily moved into and out of the recess of the workpiece, the polishing efficiency with respect to the workpiece is more enhanced.
Also, a barrel-polishing apparatus according to the eighth invention comprises a polishing medium bath with polishing mediums received therein, a base, a slide plate mounted on the base such that the slide plate is reciprocally moved in a direction of the polishing medium bath by reciprocal means, an electrically-operated rotational drive means mounted on the slide plate, a rotary shaft mounted on the electrically-operated rotational drive means and extending in a direction of reciprocal movement of the slide plate, and a workpiece attachment device mounted on a distal end portion of the rotary shaft and adapted to attach a workpiece to the rotary shaft, wherein the barrel-polishing apparatus further comprises a control unit for controlling a reciprocal movement of the reciprocal means by detecting an electric current supplied to the electrically-operated rotational drive means. Accordingly, when the rotary torque of the workpiece in the polishing mediums is reduced to reduce the electric current supplied to the electrically-operated rotational drive means, the workpiece can be moved in the polishing mediums in such a manner as to increase the rotary torque. On the other hand, when the rotary torque of the workpiece in the polishing mediums is increased to increase the electric current supplied to the electrically-operated rotational drive means, the workpiece can be moved in the polishing mediums in such a manner as to reduce the rotary torque. Therefore, with use of this barrel-polishing apparatus, a constant rotary torque can normally be obtained even if the aggregate of polishing mediums is partly worn. Thus, a constant polishing effect can be obtained efficiently and automatically.
If the slide plate is moved towards the polishing medium bath when the electric current supplied to the electrically-operated rotational drive means is smaller than a reference electric current and the slide plate is moved away from the polishing medium bath when the electric current supplied to the electrically-operated rotational drive means is larger than the reference electric current, the workpiece can easily be moved in the less-worn polishing mediums when the rotary torque is reduced and the workpiece can easily be moved in the more-worn polishing mediums when the rotary torque is increased.
Also, if the base is slanted downwardly towards the polishing medium bath, the workpiece can easily be moved reciprocally with respect to the polishing medium bath.